"Sam [Heughan] and I fought to keep the [pregnant] belly bump in — because why don't you see that in a sex scene? Why should that be a taboo? You see so many boobs all over the bloody TV."

At first glance, the premise behind Outlander — the hour-long series now in its second season on Starz — sounds kind of ridiculous. A married World War II nurse time travels back to mid-1700s Scotland, falls in love with a rugged, dashing Highland warrior and becomes involved with the Jacobite uprising against the British? Huh? Based on the popular Diana Gabaldon book series — the first of which was released 25 years ago (and is still going) – there's far more to this fantastical time-traveling historical bodice ripper than kilts and corsets. Full of bold, erotic and unflinching storytelling, it's easily one of the most substantive guilty pleasures on television.

And it hasn't been without a little controversy. For starters, the violence easily rivals that of Game of Thrones – at one point, the show's Scottish hero, Jamie Fraser, takes a whipping so brutal that his flesh peels away from his back. Plus there's the sex, and lots of it; a first-season episode featured not one, not two, but three extensive hot-and-heavy scenes, the first of which featured its era-hopping heroine Claire Randall Fraser deflowering her hunky Highlander on their wedding night. Gird your loins, for they will be on fire.

At the center of it all is Irish actress Caitriona Balfe, who's performance as Fraser is radiant, brave, beguiling, and more than deserving of her Golden Globe nomination. Now midway through Outlander's second season (with at least two more confirmed seasons on the way), Rolling Stone chatted with the breakout star about the show's success, its bold approach to sex and violence – including a particularly notorious, horrific rape scene — and whether trying to stop history from unfolding is such a great idea.

Were you a fan of the Diana Gabaldon series before you started working on the show?When I first got the audition, I didn't even know about the books. I had two scenes sent to me, and you don't really get full context. But as soon as I found out that I was going to be testing, I went out to my local bookstore in L.A., Book Soup, and grabbed a copy of the first novel; the guy at the counter was like, "Oh, you know they're going to make a TV show out of this." And I was like "Oh really?" It was quite a lucky omen.

What did you think of Claire?She's one of those great female characters — she's funny, she's kind of stubborn, she's hot-headed but she's also very empathetic, very intelligent. She just felt like a very well-rounded, fully-formed character. It felt like it would be a really exciting experience to portray her.

The book series has been around for 25 years and has a pretty diehard fanbase.I think if I had been aware of the magnitude of the fanbase and all of their expectations, I would have probably stumbled or been a little overwhelmed by it all. It was nice to go into it not knowing — then my Twitter account started exploding.